The invention relates to a weaving machine comprising a spreader for the manufacture of a fabric.
The quality of fabrics produced on weaving machines is decisively affected by the goods spreader of the weaving machine, said spreader having the task of counter-acting the lateral shrinkage tendency of the fabric. To accomplish this, there are currently two types of spreaders that are used in practical applications, namely, the cylindrical spreader that is used to grasp and laterally stretch the fabric edge by means of rotatably supported wheels with pins in a positive-locking manner, and the rod spreader that is used to hold the fabric guided around a clamping rod that is located behind a slit defined in the spreader table. Such a rod spreader has been disclosed by document EP 1 308 546 B1, for example. This publication also discloses the possibility of replacing the rod spreader with a cylindrical clamping jaw that is pressed against a friction surface.
Cylindrical spreaders lead to a not always quite negligible stress of the manufactured fabric and can result in weaving flaws if the adjustment is wrong. Still, they have largely been successful. In contrast, rod spreaders are currently only used for a few types of fabric.
The operation of the spreader must be carefully adjusted to the fabric to be produced in order to ensure the desired fabric quality.
The rod spreader does not exert a laterally tensioning effect on the fabric. Consequently, said spreader can hold the fabric web only across a width prespecified by the reed and must thus be arranged in the immediate vicinity of the beat-up point or the fabric binding point. The fabric is clamped in place in the rod spreader due to the longitudinal pull exerted on the fabric. While the read comes into abutment, the fabric section—the so-called fabric leader—between the beat-up point and the rod spreader is pushed toward the rod spreader and thus briefly stops said spreader's clamping action. In this manner, the rod spreader operates in a manner that is gentle on the fabric and, as it were, in an independent automatic manner. However, this detachment operation must be carefully adjusted by means of the appropriate longitudinal pull and the appropriate clamping rod diameter. In so doing, varying the clamping rod diameter with a spreader profile that remains otherwise the same represents a relatively significant manual effort that can lead to considerable downtimes. In practical terms, a frequent exchange of the clamping rod in order to vary the force relationships on the goods spreader is thus out of the question.
Furthermore, rod spreaders do not have reverse motion capability. In case of warp thread breakages, trouble-shooting is usually required in that the fabric is briefly moved in reverse, the problem is eliminated, and the fabric is returned into its old position. This requires that the fabric transport may occur in forward and backward direction. However, for function-specific reasons, the rod spreader is only capable of intermittent transport only in forward direction at the time of weft beat-up.
Due to the aforementioned problems regarding the adjustment of the correct clamping force as a function of the correct fabric pull, rod spreaders have become less ubiquitous in the past, even though—in principle—a rod spreader is capable of holding the fabric in a non-destructive manner at a width that that has been prespecified by the reed, i.e., of preventing the fabric's lateral contraction. In contrast, cylindrical spreaders actively impart the fabric with a transverse tension and can thus result in high stress on the fabric.
Therefore, it is the object of the invention to provide a weaving machine with a goods spreader that is simple in construction, operates reliably and can be adjusted in the easiest possible manner.